what is downbearing?

[Stéphane Collin]

Hello Dave.

I liked your post.  Finally someone accepting that theory, so far, has a
hard time to coincide with real world.  Sometimes difficult to say in front
of technicians.

Stéphane Collin.

----- Original Message ----- 
From: "Dave Nereson" <davner@kaosol.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Friday, February 20, 2004 9:25 AM
Subject: Re: what is downbearing?


.
>      It has nothing to do with the physical playability of the piano, that
> is, the action, or "touch", but has a lot to do with volume and sustain.
> Supposedly.  Some pianos have no downbearing, yet still have plenty of
> volume and sustain.  Supposedly more bearing means louder volume and less
> sustain; less bearing (strings closer to being in a straight line) means
> more sustain and less volume.  But this isn't always the case.  Too many
> other factors enter in, such as the crown (upward bowing, or curvature) of
> the soundboard, the quality of the wood, the density of the grain, the
> resonance of the rim or case, the various qualities of the hammers and
their
> voicing (especially), and to a smaller degree, action regulation and the
> "touch" of the player.
>     It can be measured as a downward angle of deflection in degrees, or by
> the amount the string "goes downhill" from the rear bridge pin to the
> aliquot (if present) or hitch pin.  Others have said downbearing is the
> downward pressure of the strings on the bridge.  Well, yes, but that's not
> what we measure.   It's the downward deflection in thousandths of an
inch -- 
> maybe even a sixteenth or an eighth in extreme cases, or the angle in
> degrees -- maybe a half a degree to as much as five (?) degrees that we
> measure, not the pressure in pounds of all the strings pressing on the
> bridge.
>     If you're looking at a used piano for someone and it has no
downbearing,
> it could be that the soundboard has lost its crown.  (That's better
checked
> by stretching a string tautly across the bottom or back of the
soundboard -- 
> lengthwise, between the longest ribs -- and see if there's a gap in the
> middle between the string and the board.)  It's a concern -- a small one
if
> the tone and sustain of the piano is still good or great; and perhaps a
> larger concern if the piano is almost new.
>     As far as formulae and what it all means -- this is more thoroughly
> covered in articles about soundboard replacement, bridge recapping, etc.
by
> Nick Gravagne and many others in the PTG Journal.
>     --David Nereson, RPT
>
>
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